ANDERSON, Ind. (AP) - Signing players has suddenly become a No. 1 priority for the Colts.

On Tuesday, the Colts signed their first-round pick, left tackle Anthony Castonzo, and free agent linebacker Ernie Sims, Detroit's first-round pick in 2006. Those moves come less than 24 hours after Indy signed another former first-rounder, defensive lineman Jamaal Anderson.

Castonzo was taken 22nd overall, is expected to protect Peyton Manning's blind side and was the last unsigned pick in the Colts' draft class.

While the Castonzo move was expected, Indy's uncharacteristic free agent frenzy was not. Only one other player on the current roster, kicker Adam Vinatieri, joined Indy as an unrestricted free agent. Agent Todd France said Sims has a one-year deal, and there's no telling if the Colts are finished.

"It just depends on what we're looking for," coach Jim Caldwell said after Tuesday's special teams practice. "You want someone that can have an impact and someone that fits what we do. So we take all of those things into consideration."

Sims looks like a perfect fit with the Colts, whose defense has traditionally favored speed over size.

At 6 feet, 230 pounds, Sims is almost a carbon copy of Clint Session, a three-year starter who signed a five-year deal with division rival Jacksonville last week. Session was listed at 6-0, 235 pounds.

Plus, Sims could earn the starting job on the weak side.

Second-year linebacker Pat Angerer and fourth-year linebacker Philip Wheeler will battle for the starting strong side job. Wheeler has 13 career starts, all at that spot, while Angerer finished his rookie season as Indy's second-leading tackler (88) and played a little of everything.

Nine-year veteran and defensive captain Gary Brackett will man the middle.

But the big battle could come down to Sims and Kavell Conner, a second-year player who started nine games and had 47 tackles as a rookie.

The question now is what more might the Colts do?

When asked Tuesday morning if Indy was looking at any more free agents, Caldwell smiled and said: "There's a couple."

That's a drastic change for a team that prefers keeping the players it develops rather than signing someone else's.

It is also in an indication of how much wiggle room under the $120.3 million salary cap the Colts created by re-signing Manning to a five-year, $90 million, cap-friendly deal.

A week ago, team owner Jim Irsay acknowledged the Colts would likely have to release some players. Indy had budgeted $23.1 million to keep the four-time league MVP under the franchise tag, but the new deal reduced his cap number to $16 million.

Indy also created additional room by redoing the contract of right tackle Ryan Diem.

So far, only one veteran player has been released in a cost-cutting move -- starting cornerback Kelvin Hayden. Session and free agent left tackle Charlie Johnson both signed with new teams.

Castonzo, the 6-7, 305-pound tackle is expected to fill the vacancy left by Johnson's departure. He started a record 54 games at Boston College and was a third-team All-American last season. The contract holdout kept Castonzo out of two light practices Monday and a special teams workout Tuesday. Castonzo did partice Tuesday afternoon.

"I am excited to get into camp and get to work with my teammates," Castonzo said in a statement issued by the team. "I know there is a lot for me to learn and I am going to do whatever I can to get on the field."

Caldwell said he was the only draft pick who had been given a playbook. He got that during the brief period when the lockout was lifted in April.

Sims and Anderson watched the afternoon practice. NFL rules do not allow veteran free agents to practice until later this week.

Sims was Detroit's first-round pick, No. 9 overall, in 2006. He started every game his first three seasons in Detroit, recording more than 100 tackles each year and posted a career-high 134 tackles in 2007. But injuries limited him to only eight starts in 2009 and a career-low 49 tackles. In April 2010, he was sent to Philadelphia in a three-way trade. He started 15 games in 2010 and finished with 55 tackles.

In five seasons, the 26-year-old Sims has 475 total tackles, 41/2 sacks and 1 interception.

Anderson, 25, is also trying to jump-start his career in Indy. The 6-6, 289-pound defensive lineman was Atlanta's first-round choice, No. 8 overall, in 2007, but was cut Saturday.

Indy has been looking for depth along the line and trying to upgrade its run defense for years. With the Falcons, Anderson was known as a better run stopper than pass rusher, and the Colts hope Anderson and Sims are still young enough to meet the lofty expectations their former teams had after drafting them in the top 10.

Indianapolis also waived linebacker Darry Beckwith to open a roster spot Tuesday.